Lithography techniques include processes in which, for example, a resist film formed from a resist material is formed on top of a substrate, the resist film is selectively exposed with irradiation such as light, an electron beam or the like through a mask in which a predetermined pattern has been formed, and a developing treatment is then conducted, thereby forming a resist pattern of the prescribed shape in the resist film. Resist materials in which the exposed portions change to become soluble in the developing liquid are termed positive materials, whereas resist materials in which the exposed portions change to become insoluble in the developing liquid are termed negative materials.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of miniaturization.
Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use F2 excimer lasers, electron beams EB), extreme ultraviolet radiation (EUV) and X-rays.
Conventionally, as the negative resist compositions used for processes that employ i-line radiation or a KrF excimer laser (248 nm) as the light source, negative resist compositions including a combination of an acid generator, an alkali soluble resin such as a novolak resin or a polyhydroxystyrene, and an amino-based resin such as a melamine resin or a urea resin have been used (for example, see patent reference 1).
Moreover, as negative resist materials for a process using an ArF excimer laser with a shorter wavelength, negative resist compositions including a resin component containing a carboxyl group, a cross-linking agent containing an alcoholic hydroxyl group, and an acid generator have been proposed as those wherein transparency to an ArF excimer laser can be improved. These compositions are of a type wherein the action of the acid generated by the acid generator causes a reaction between the carboxyl group of the resin component and the alcoholic hydroxyl group of the cross-linking agent, thus altering the resin component from an alkali soluble state to an alkali insoluble state.
Furthermore, a negative resist composition including a resin component containing a carboxyl group or a carboxylate ester group together with an alcoholic hydroxyl group, and an acid generator, wherein the carboxyl group or the carboxylate ester group, and the alcoholic hydroxyl group within the resin component undergo an intermolecular reaction under the action of the acid generated by the acid generator, thus altering the resin component from an alkali soluble state to an alkali insoluble state, has also been proposed (for example, see non-patent references 1 to 3 and patent reference 2).
[Patent Reference 1]
Japanese Unexamined Patent Application, First Publication No. Hei8-3635
[Patent Reference 2]
Japanese Unexamined Patent Application, First Publication No. 2000-206694
[Non-Patent Reference 1]
Journal of Photopolymer Science and Technology, Vol. 10, No. 4, pp. 579 to 584, published in 1997
[Non-Patent Reference 2]
Journal of Photopolymer Science and Technology, Vol. 11, No. 3, pp. 507 to 512, published in 1998
[Non-Patent Reference 3]
SPIE Advances in Resist Technology and Processing XIV, Vol. 3333, pp. 417 to 424, published in 1998
[Non-Patent Reference 4]
SPIE Advances in Resist Technology and Processing XIX, Vol. 4690, pp. 94 to 100, published in 2002